gistfile1.cpp

/*

  Compiling this code gives me a warning about old-style casts:

    $ g++ -Wold-style-cast -o g++-warnings-check g++-warnings-check.cpp -lz
    g++-warnings-check.cpp: In function ‘int main()’:
    g++-warnings-check.cpp:49:20: warning: use of old-style cast [-Wold-style-cast]

  "deflateInit" is actually a macro:

    #define deflateInit(strm, level) \
            deflateInit_((strm), (level), ZLIB_VERSION, (int)sizeof(z_stream))

  Which expands to the following, which indeed has an old-style cast
  in it:

    deflateInit_((&strm), ((-1)), "1.2.7", (int)sizeof(z_stream));
                                           ^^^^^^^^^^^^^^^^^^^^^

  But I thought that zlib.h would be considered a system header, so
  any macros defined in there would have immunity from most warnings.
  From the manual:

    2.8 System Headers
    ==================

    The header files declaring interfaces to the operating system and
    runtime libraries often cannot be written in strictly conforming
    C.  Therefore, GCC gives code found in "system headers" special
    treatment.  All warnings, other than those generated by `#warning'
    (*note Diagnostics::), are suppressed while GCC is processing a
    system header.  Macros defined in a system header are immune to a
    few warnings wherever they are expanded.  This immunity is granted
    on an ad-hoc basis, when we find that a warning generates lots of
    false positives because of code in macros defined in system
    headers.

  System is Fedora 18 x86-64, gcc 4.7.2, zlib 1.2.7 (both from rpm).

 */

#include <string.h>
#include <zlib.h>

int main()
{
    z_stream_s strm;
    memset( &strm, 0, sizeof( strm ) );
    const int rc = deflateInit( &strm, Z_DEFAULT_COMPRESSION );
    return rc;
}